In the exercise and rehabilitation equipment sector, machines designed to allow the user to perform aerobic exercises which "simulate" given sports or physical activities have become increasingly important, both for muscular training and for improving cardiovascular condition and general physical well-being.
For example, there are stationary machines that allow the user to perform exercises substantially comparable to riding a bicycle, climbing stairs or walking or running. The present invention relates to a treadmill, designed to allow the user to walk or run on the spot.
Machines of the afore-mentioned type use various types of devices in an attempt to recreate as faithfully as possible the actual reaction of the means with which the human body interacts, so that the exercise performed in the gym is as similar as possible to that of the activity in question. In simulating physical activity, especially in modern machines, every effort has been made to emphasise the positive aspects of the exercise and limit any disadvantages, so that the training or rehabilitation results in the user obtaining the benefits of the specific exercise, as far as possible limiting any negative characteristics involved in performing the exercise.
In the case of the example relative to the present invention, the athletic movement involved in walking and running is simulated thanks to the presence of a belt moved on pulleys and which moves in the opposite direction to that which would be followed by the treadmill user when actually performing the corresponding exercise.
One of the main disadvantages of walking and, to a greater degree, running is the shock to the body of the walker or runner caused by the reaction of the ground under foot; in other words, especially on hard surfaces, the reaction of the ground can negatively influence the exercise and in some cases causes tendon, joint and other types of pathologies.
The above-mentioned disadvantage is also encountered on treadmills of the known type. In such machines, at least in the zone designed for performance of the exercise (that is to say, the zone on which the user walks or runs) there is a board that supports the belt when a force is exerted on the latter by the user.
Given that they must support the belt, the boards normally used are made of rigid material. For this reason, when, during exercise, the user exerts a force on the belt-board assembly, the corresponding reactions may prove damaging since they are insufficiently cushioned.
In order to limit any negative effects, technical development in the exercise machine sector has contributed to the application of modifications to the board zone, attempting to dampen the reaction of the belt to the force exerted by the user.
Document U.S. Pat. No. 3,689,066 describes a treadmill in which a set of hollow elements with variable volume and with valves designed to define a sort of air cushion is applied to the board. When used, the force exerted on the board by the user and the consequent response are dampened thanks to this air cushion.
Document U.S. Pat. No. 5,454,772 describes treadmills in which resilient elastomer elements are envisaged between the base and the belt supporting board.
The reaction of the treadmill is proportional to a constant, invariable value. This means that it is impossible to vary the treadmill's response according to the type of exercise to be performed, substantially obtaining responses that are always the same for equal forces exerted.
This is a disadvantage since, with elements that have a "fixed" reaction, meaning that it is impossible to vary the elastic constant relative to the treadmill's response, it is impossible to set exercises according to important parameters, such as those listed below. These parameters, which may vary greatly, may comprise the user's physique, gait, pronation, degree of fitness, the effects of having warmed up, any problems linked to pathologies, etc.
Another attempt to overcome this disadvantage is that proposed in U.S. Pat. No. 4,350,336, which describes a treadmill with a supporting board hinged at one end of the treadmill structure, and a cushioning support, comprising rubber blocks and positioned beneath the board; the support may be moved lengthways under the board so as to vary the leverage value defined by the hinged board and, as a result, the value of the contribution of the force exerted by the user. In other words, there is a sort of trampoline resting on a wedge defined by the cushioning support with fixed elastic constant and, in an attempt to obtain a different response to the action of the user, the contribution of the action itself is varied rather than the elastic reaction of the support; thus, with reference to the lever formed by the trampoline, the point in which the resistance is exerted (elastic reaction of the support) is moved, without changing the type of resistance offered.
The technical sector for treadmills is overcrowded with a large number of technical solutions for specific aims and/or the production of details.